PENGECUALIAN ATURAN OKTET DAN POLARISASI IKATAN KOVALEN

Summary

In this chemistry lesson, Mrs. Cica explains two crucial concepts: exceptions to the octet rule and polarization of covalent bonds. She covers how some compounds don't follow the octet rule, including those with fewer than eight electrons, odd valence electrons, or expanded octets. The lesson also explores polarization, where differences in electronegativity between bonded atoms lead to polar and nonpolar covalent bonds. Key factors like electronegativity, lone pairs, and molecular symmetry are highlighted to determine whether a bond is polar or nonpolar. This engaging lesson provides clear examples and visual aids to help students grasp complex chemical concepts.

Takeaways

• 😀 The lesson covers two main topics: exceptions to the octet rule and the polarization of covalent bonds.
• 😀 The octet rule is explained, with elements aiming to reach a stable electron configuration of 8 valence electrons (octet) or 2 valence electrons (duplet for hydrogen).
• 😀 There are three exceptions to the octet rule: compounds that don’t reach the octet, compounds with odd valence electrons, and compounds with an expanded octet.
• 😀 In compounds that don't reach the octet, the central atom may have fewer than four valence electrons, like in BCl3, where B only has 6 valence electrons after bonding.
• 😀 Compounds with odd valence electrons, like NO2, can occur, where the central atom has an odd number of electrons (e.g., nitrogen in NO2 has 7 electrons after bonding).
• 😀 Expanding the octet happens when the central atom can accommodate more than 8 electrons in its outer shell, such as in PCl5, where phosphorus has 10 valence electrons.
• 😀 Polarization of covalent bonds occurs due to differences in electronegativity between bonded atoms, causing a shift in electron density.
• 😀 Polar covalent bonds create positive and negative poles, like in HCl, where chlorine is more electronegative than hydrogen, resulting in a polarized bond.
• 😀 Nonpolar covalent bonds occur when there is little or no difference in electronegativity between atoms, as in H2, where both atoms are hydrogen with identical electronegativity.
• 😀 Molecules are classified as polar or nonpolar based on the difference in electronegativity, with polar molecules having a significant electronegativity difference.
• 😀 The central atom's presence or absence of lone electron pairs (PB) can determine if a molecule is polar or nonpolar, with molecules having PB generally being polar.

Q & A

What is the main topic of the video?

The main topic of the video is the exception to the octet rule in chemistry, as well as the polarization of covalent bonds.

What are the two types of chemical bonds discussed in the video?

The two types of chemical bonds discussed are ionic bonds and covalent bonds.

What happens during an ionic bond?

An ionic bond occurs between metal and non-metal elements, where electrons are transferred. Metals release electrons, and non-metals accept them, resulting in a stable bond.

What is the octet rule?

The octet rule states that elements tend to bond in a way that their valence electron shell is filled with eight electrons (or two electrons in the case of hydrogen and helium).

What are the three exceptions to the octet rule?

The three exceptions to the octet rule are: 1) The compound does not reach the octet, 2) The compound has odd valence electrons, 3) The compound has an expanding octet.

Can you explain the exception where the compound does not reach the octet?

This occurs when the central atom has fewer than four valence electrons, so even after bonding, it cannot achieve the octet configuration. An example is BCl3, where the central boron atom only has six valence electrons after bonding.

What is an example of a compound with odd valence electrons?

An example is NO2, where nitrogen has five valence electrons and oxygen has six. After bonding, the nitrogen atom has an odd number of valence electrons, making it an exception to the octet rule.

What does it mean when a compound has an expanding octet?

An expanding octet occurs when the central atom is from period 3 or higher, and it can accommodate more than eight electrons in its outer shell. For example, PCl5 has 10 valence electrons around the phosphorus atom, exceeding the octet.

What is polarization in covalent bonds?

Polarization occurs due to differences in electronegativity between bonded atoms. The atom with higher electronegativity attracts electrons more strongly, resulting in a partial negative charge, while the atom with lower electronegativity becomes partially positive.

How do you determine if a covalent bond is polar or nonpolar?

A covalent bond is polar if there is a significant difference in electronegativity between the bonded atoms, creating positive and negative poles. If the electronegativity difference is small or zero, the bond is nonpolar.

Can you give an example of a polar and nonpolar covalent compound?

An example of a polar covalent compound is HCl, where chlorine is more electronegative than hydrogen, creating a polar bond. An example of a nonpolar covalent compound is H2, as both hydrogen atoms have the same electronegativity.

What is the role of lone pairs (PBE) in determining whether a molecule is polar or nonpolar?

The presence of lone pairs (PBE) on the central atom can make a molecule polar because they affect the symmetry of the molecule. If the central atom has lone pairs, the molecule is likely polar. If there are no lone pairs and the molecule is symmetric, it is nonpolar.